In a liquid crystal display device, pixels having a pixel electrode and a thin film transistor (TFTs) are arranged in a matrix form in a TFT substrate. Further, color filters and the like are formed in a counter substrate at locations corresponding to the pixel electrodes of the TFT substrate. The counter substrate is disposed opposite to the TFT substrate with a liquid crystal sandwiched between the TFT substrate and the counter substrate. Then, an image is formed by controlling the amount of light transmitted through the liquid crystal molecules for each pixel.
The use of the liquid crystal display device is growing in various fields due to its flatness and light weight. Compact liquid crystal display devices are widely used in electronic devices such as mobile phones and digital still cameras (DSC). The liquid crystal display panel does not emit light by itself, so that it is necessary to have a backlight. If the light from the backlight is not completely blocked in black display, the contrast of the screen is degraded.
Various methods have been developed to increase the contrast, such as the use of a light shielding film and a black matrix. However, in the vicinity of the end face of the liquid crystal display panel, it is difficult to form a light shielding film with high reliability, and there is a problem of light leakage from the backlight in the periphery of the screen. In order to prevent the light leakage from the backlight in the periphery of the screen, Japanese Patent Application Laid-Open No. 2012-32506 describes a structure in which a light-shielding seal material is formed to the edge of the liquid crystal display panel.
Meanwhile, in order to increase the reliability of the liquid crystal display panel, it is important to ensure the reliability of the seal portion for isolating the inside filled with the liquid crystal from the outside. There are lead lines extending from the inside to the outside through the seal portion in order to provide scan signals and image signals to pixels. At this time, the distance between the TFT substrate and the counter substrate is different in the area where the lead lines exist and in the area where the lead lines do not exist. In order to equalize the distance between the TFT substrate and the counter substrate, a dummy metal may be provided in the area where the lead lines do not exist.
Japanese Patent Application Laid-Open No. 2005-283862 describes a structure in which, a slit is formed between metals without forming the dummy metal on the entire surface of the area where the lead lines do not exist. With this structure, it is possible to reduce the influence of the occurrence of static electricity, and to detect defects in the seal material through the slit.